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Citrus Tech Forum: Boosting brix through deficit irrigation

21 December 2018

Leeton grower Dean Morris, Moricom Orchards, said he had a gut feel he could use deficit irrigation to increase brix on very vigourous rootstocks. He was correct and even though he has refined his technique over the years, he still relies on that gut feel every year. Mr Morris will expand on his technique at the 2019 Citrus Tech Forum in Adelaide. NSW DPI researcher Tahir Khurshid, who is now undertaking research on deficit irrigation to improve flavour profiles, will also discuss his research. Mr Morris planted 40ha of Afourers in 2007, planting 20Ha on vigorous rootstock such as Rough Lemon and Macrophylla and 20 Ha on traditional rootstocks The theory was fruit on the vigorous rootstock would mature earlier, enabling them to pick the same variety for 12 weeks. “I had an inkling we could get 12 brix or better by reducing the water applied for the last 12 weeks,” Mr Morris said. “I’d also learnt from Andrew Harty when he was in New Zealand, growing Satsuma mandarins for the Japanese market, and had further discussions with Professor Martinez (of Spain).” Mr Morris said with trial and error, they achieved the minimum target of 12 brix for the brand. “We achieved high fruit yields with acceptable taste to the trade and better fruit size. The same method on traditional rootstock saw us achieve from 14-19 brix for Afourer, which is five above average.” Trees are planted on large mounds, with two drippers per tree, providing complete control when water is turned off. “Roots are in the top 40 cm of soil so they’re not affected by large amounts of rainfall. We had 700mm in June-July-August in 2016 and still met the target.” Although Dr Khurshid’s research is ‘fine tuning’ methods employed by Mr Morris and other growers, Mr Morris said he still relies on “gut feel”. “I look at the tree, taste the fruit, and if fruit is getting soft, I turn the water back on.” The technique saves 1Meg of water/ha, cuts power costs, does not affect fruit size and causes minimal fruit drop. He has consistent yields and little biannual bearing. Mr Morris said the practice is becoming common in the US and other countries and believes every Australian grower must continually improve fruit quality to maintain our industry advantage over competitors. “We’re probably not getting a premium for 16-17 brix but that’s a marketing issue. We need a critical mass to make an impression. “Our biggest threat are our overseas competitors. South American countries will take us out of China like they did in the US if we don’t improve. “If we do nothing and rest on our laurels, everyone will catch up. Others will be $8 cheaper and taste just as good. “How can we send 9 to 12 brix in fruit, the same as our competing countries, and expect a premium?”

To register for the 2019 Citrus Technical Forum, to be held in Adelaide on March 6-7, visit here.